Acta Crystallographica Section B

Structural Science

Volume 55, Part 6 (December 1999)

research papers

Acta Cryst. (1999). B55, 947-952 [ doi:10.1107/S0108768199005698 ]

Preparation and characterization of tetrachlorocobaltates(II) of ,-alkylenediammonium. Magnetic and thermal properties. Crystal structure of [NH₃(CH₂)₅NH₃]CoCl₄

J. J. Criado, A. Jiménez-Sánchez, F. H. Cano, R. Sáez-Puche and E. Rodríguez-Fernández

Abstract: Tetrachlorocobaltates(II) of diprotonated [alpha] , [omega] -diaminoalkanes with the formula [NH₃(CH₂)_nNH₃]CoCl₄, where n = 5 (cadaverine; 1,5-pentanediammonium tetrachlorocobaltate), 8 (1,8-octanediammonium tetrachlorocobaltate) and 10 (1,10-decanediammonium tetrachlorocobaltate), were prepared. The compounds were studied by mass spectrometry, FT-IR and visible spectroscopy, magnetic susceptibility techniques and thermal analysis. The compounds contain the tetrahedral tetrachlorocobaltate(II) ion and the corresponding diprotonated diamine (cadaverine, 1,8-octamethylenediamine and 1,10-decamethylenediamine). The compound corresponding to cadaverine crystallizes in the monoclinic space group P2₁/c, with lattice parameters a = 7.1633 (7), b = 15.940 (3), c = 11.137 (2) Å, [beta] = 98.44 (1)° and Z = 4. Its crystal structure contains slightly distorted tetrahedral CoCl $_4^{2-}$ ions: the largest difference in Co-Cl bond lengths is 0.029 Å and the largest difference in Cl-Co-Cl angles is 7.76°. The compound also contains diprotonated cadaverine ions. An extensive hydrogen-bonding network connects these ions. The slightly positive deviations of the magnetic susceptibility from the Curie-Weiss law are in agreement with the ⁴A₂ ground state for the tetrachlorocobaltate anion. The compounds with eight and ten C atoms show phase transitions in the solid state and a greater complexity is observed in their differential scanning calorimetry curves. Unfortunately, no suitable single crystals of these could be obtained.

Keywords: Tetrachlorocobaltates; Magnetic properties; Thermal properties.